slideshow: run a slideshow' or main' submodule, if any

A common Slideshow pattern is to put a subset of slides in its
own module with a `run-slides' function, and then you'd
(un)comment a `(run-slides)' call at the end of the module to
work on the subset by itself. Now, you can write
`(module+ main (run-slides))' atthe end of the module and not
have to comment it out. Adding `main' support to the `slideshow'
executable makes it more consistent with using `racket' directly.
Checking first for a `slideshow' submodule makes it possible
for `slideshow' and `racket' to do different things, in case
that's useful.

collects/scribblings/slideshow/guide.scrbl

@@ -219,10 +219,11 @@ displays).
 
 @defmodule[slideshow/start]
 
-The @exec{slideshow} executable invokes the
+The @exec{slideshow} executable instantiates the
 @racketmodname[slideshow/start] module, which inspects the command
 line as reported by @racket[current-command-line-arguments] to get
-another module to provide the slide content. It also initializes
+another module to @racket[require] for the slide content.The @racketmodname[slideshow/start]
+module also initializes
 variables like @racket[printing?] and @racket[condense?] based on
 flags supplied on the command line.
 
@@ -233,7 +234,14 @@ command
 
 runs the slides.
 
-The @exec{Slideshow} executable accepts a number of command-line
+If the module given to @exec{slideshow} has a @racketidfont{slideshow}
+submodule, then @racketmodname[slideshow/start] @racket[require]s the
+@racketidfont{slideshow} submodule after @racket[require]ing the
+module. If the module has no @racketidfont{slideshow} but has a
+@racketidfont{main} submodule, then the @racketidfont{main} submodule
+is @racket[require]d.
+
+The @exec{slideshow} executable accepts a number of command-line
 flags.  Use the @DFlag{help} flag to obtain a list of other
 flags.
 

collects/slideshow/cmdline.rkt

@@ -4,7 +4,7 @@
            mzlib/file
            mzlib/contract
            mred
-           mzlib/cmdline
+           racket/cmdline
            texpict/mrpict
            texpict/utils
            mzlib/math
@@ -57,10 +57,9 @@
     
     (define file-to-load
       (command-line
-       "slideshow"
-       (current-command-line-arguments)
-       [once-each
-	(("-M" "--monitor") monitor "display to <monitor> (count from 0)"
+       #:program "slideshow"
+       #:once-each
+       (("-M" "--monitor") monitor "display to <monitor> (count from 0)"
 	 (let ([n (string->number monitor)])
 	   (unless (and n (exact-nonnegative-integer? n))
 	     (die 'slideshow "argument to -M is not an exact non-negative integer: ~a" monitor))
@@ -102,16 +101,6 @@
         (("-m" "--no-smoothing") 
          "disable anti-aliased drawing (usually faster)"
          (set! smoothing? #f))
-        ;; Disable --minutes, because it's not used
-        #;
-        (("-m" "--minutes") min "set talk duration in minutes"
-        (let ([n (string->number min)])
-        (unless (and n 
-        (integer? n)
-        (exact? n)
-        (positive? n))
-        (die 'slideshow "argument to -m is not a positive exact integer: ~a" min))
-        (set! talk-duration-minutes n)))
         (("-i" "--immediate") "no transitions"
          (set! use-transitions? #f))
         (("--trust") "allow slide program to write files and make network connections"
@@ -131,20 +120,12 @@
         (("--comment-on-slide") "display commentary on slide"
          (set! commentary? #t)
          (set! commentary-on-slide? #t))
-        (("--time") "time seconds per slide" (set! print-slide-seconds? #t))]
-       [args slide-module-file
-             (cond
-              [(null? slide-module-file) #f]
-              [(null? (cdr slide-module-file)) 
-               (let ([candidate (car slide-module-file)])
-                 (unless (file-exists? candidate)
-                   (die 'slideshow "expected a filename on the commandline, given: ~a"
-                        candidate))
-                 candidate)]
-              [else (die 'slideshow
-                         "expects at most one module file, given ~a: ~s"
-                         (length slide-module-file)
-                         slide-module-file)])]))
+        (("--time") "time seconds per slide" (set! print-slide-seconds? #t))
+        #:ps
+        "After requiring <slide-module-file>, if a `slideshow' submodule exists,"
+        " it is required. Otherwise, if a `main' submodule exists, it is required."
+        #:args ([slide-module-file #f])
+        slide-module-file))
 
     (define printing? (and printing-mode #t))
 

collects/slideshow/start.rkt

@@ -64,7 +64,15 @@
 			    (lambda (who where-name where-port-num mode)
 			      (error 'slideshow
 				     "slide program attempted to make a network connection")))))
-    (dynamic-require (path->complete-path content) #f))
+    (define content-path (path->complete-path content))
+    (dynamic-require content-path #f)
+    (ormap (lambda (sm)
+             (define submod-path `(submod ,content-path ,sm))
+             (and (module-declared? submod-path #t)
+                  (begin
+                    (dynamic-require submod-path #f)
+                    #t)))
+           '(slideshow main)))
 
   (when (file-to-load)
     (load-content (string->path (file-to-load))))

doc/release-notes/racket/HISTORY.txt

@@ -5,6 +5,7 @@ Added raise-argument-error, raise-result-error,
 racket/contract: added procedure-arity-includes/c
 racket/sandbox: added sandbox-propagate-exceptions
 racket/cmdline: add #:ps for command-line
+slideshow/start: run a `slideshow' or `main' submodule, if any
 Changed impersonate-struct so that accessor impersonation requires
  work only if the field is accessible via the current impersonator
  or a mutator for the same field is also impersonated